you have a biter... Tailbitting can be caused by stress, boredom, and hunger. I'm not sure what you can do to stop it but try to move his "accessories" in his tank around to keep him from getting bored. Also try putting a pingpong ball or something inside to keep hi, busy. Feed regularly and make sure youlre keeping his water&everyhing clean to keep from stress

They do it when they are bored of their food. Try switching it up! Like feeding it pellets today, a brine shrimp tomorrow, and a flake the next day! It will make him less worried about his tail and more on his food! They also do it when you feed to less, 3-4 big pellets or flakes each day a week or 8 little pellets a day. I did not include fasting lol.

That is why I said not including fasting. They say feed what you can in 2-3 minutes. I know what I do. Little pellets are small! Tinier than a betta's pupil. I said Three to Four but two is safer. Three a day with 1 day fasting a week is enough. 6 little betta pellets is better.